This invention relates to composite material articles and processes for their manufacture, and more particularly to seamless metal-clad filament-reinforced resin matrix composite tubular structures and processes for their manufacture.
Composite materials have great potential for solving challenging and often critical problems in the design of spacecraft and space structures. Mission objectives often impose severe requirements for dimensional stability over a wide range of temperatures, minimum weight, low cost, high stiffness and strength, thermal and electric conductivity and, more recently, the capability to withstand laser and nuclear threats. Probably the greatest constraint upon long orbital life for spacecraft is the susceptibility to attack by atomic oxygen in low earth orbit.
Composite materials offer specific strength, specific rigidity and thermal expansion characteristics that are superior to metallic materials; however, possessing strength and other properties in one primary direction, they lack transverse properties including torsion. Furthermore, conventional graphite-epoxy orientation mix constructions suffer from deleterious hygroscopic effects, such as moisture absorption and desorption, which effect dimensional change. A related serious problem is outgassing of condensable organic constituents, which will condense and deposit on critical surfaces in a space environment. In addition, a process must be provided for shielding ultraviolet radiation to protect the organic matrix from deleterious exposure, and for providing electrical conductivity to preclude static charging in space.
Metal-clad composites make a significant advancement over those composite systems being used for both spacecraft and aircraft; however, the material consolidation and tooling advances necessary to realize the potential of such metal-clad composites have not hitherto been achieved. Prior methods have involved tape-wrapping a metal foil, or spraying or depositing a thin metallic film on the fiber reinforced composite structure surfaces. Such methods suffer from lack of adhesion between the metal surface and the composite, porosity of surface, and high cost; and these methods have resulted in a product which is difficult to join to other structures and is non-tunable to precise thermal dimensional stability after manufacturing.
Accordingly, it is an object of this invention to provide an efficient method of producing seamless metal-clad composite structures.
A further object of this invention is to improve circumferential heat transfer in seamless metal-clad composite structures to reduce thermal stress to acceptable levels for the space environment, and to reduce thermal distortion of the structures due to circumferential temperature gradients.
A further object of this invention is to shield the organic matrix of a metal-clad composite structure from deleterious exposure due to ultra-violet radiation and to provide electrical conductivity to preclude static charging.
A further object of this invention is to provide a method of sealing and isolating the organic matrix of a metal-clad composite structure to preclude vaporization of condensable solids which will coat optical sensor and optical reflective surfaces.
A further object of this invention is to provide a method of toughening composite laminates of a metal-clad composite structure against mechanical impact damage.
A further object of this invention is to provide a method of hardening exposed surfaces of a metal-clad composite structure against directional radiant heating, such as laser, by providing transverse circumferential heat transport.
A further object of this invention is to provide a highly conductive surface of a metal-clad composite structure to dissipate or inhibit electron emission through a boundary.
A further object of this invention is to provide protection to the organic matrix of a metal-clad composite structure against deleterious attack by atomic oxygen.
Other objects and advantages of this invention will become apparent hereinafter in the specification and drawings which follow.